Preparation Method for Pyrrolidine-2-Carboxylic Acid Derivatives

(19) TZZ¥Z__T

(11) EP 3 015 456 A1

(12) EUROPEAN PATENT APPLICATION published in accordance with Art. 153(4) EPC

(43) Date of publication: (51) Int Cl.: 04.05.2016 Bulletin 2016/18 C07D 207/22 (2006.01) C07D 207/46 (2006.01) C07D 207/16 (2006.01) (21) Application number: 14816731.5 (86) International application number: (22) Date of filing: 23.06.2014 PCT/CN2014/080520

(87) International publication number: WO 2014/206257 (31.12.2014 Gazette 2014/53)

(84) Designated Contracting States: • LI, Yuanqiang AL AT BE BG CH CY CZ DE DK EE ES FI FR GB Taizhou GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Zhejiang 318000 (CN) PL PT RO RS SE SI SK SM TR • CHE, Daqing Designated Extension States: Taizhou BA ME Zhejiang 318000 (CN) • QIAN, Lingfeng (30) Priority: 26.06.2013 CN 201310261857 Taizhou 19.11.2013 CN 201310580894 Zhejiang 318000 (CN) 10.06.2014 CN 201410255311 • ZHU, Guoliang Taizhou (71) Applicant: Zhejiang Jiuzhou Pharmaceutical Co., Zhejiang318000 (CN) Ltd. • YE, Wenfa Jiaojiang District Taizhou Taizhou City Zhejiang 318000 (CN) Zhejiang 318000 (CN) (74) Representative: Pharma Concepts GmbH (72) Inventors: Unterer Rheinweg 50 • ZHANG, Bin 4057 Basel (CH) Taizhou Zhejiang 318000 (CN)

(54) PREPARATION METHOD FOR PYRROLIDINE-2-CARBOXYLIC ACID DERIVATIVES

(57) The present invention relates to the field of medical synthesis, in particular to a preparation method for pyrrolidine-2-carboxylic acid derivatives. The present invention adopts the following technical solution: providing a compound having a structure of formula (E), wherein

R is R1 or R2, R1 is C1-C6 an alkyl, benzyl, p-methoxybenzyl, or p-nitrobenzyl group, and R2 is hydrogen; R3 is a protecting group of the carboxyl group; and P1 is a protecting group on nitrogen. EP 3 015 456 A1

Printed by Jouve, 75001 PARIS (FR) EP 3 015 456 A1

Description

[0001] This application claims the priority of China Patent Application No. 201310261857.4, 201310580894.1 and 201410255311.2 filed with the Patent Office of China on June 26, 2013, November 19, 2013 and June 10, 2014 suc- 5 cessively titled "Preparation method for pyrrolidine-2-carboxylic acid derivatives", the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

10 [0002] The present invention relates to the field of medical synthesis, in particular to a preparation method for pyrrolidine- 2-carboxylic acid derivatives.

BACKGROUND OF THE INVENTION

15 [0003] The following compound Z is the most common intermediate used in the field of medical synthesis,

Wherein Y is a hydrogen atom or C1∼C6 alkyl. M is a hydrogen atom or a protecting group on nitrogen. X is a hydrogen atom or a protecting group of carboxyl. 30 [0004] Currently, there are a limited number of routes for preparing the above-mentioned compound, in which the yields are mostly low and the starting material is difficult to be produced. [0005] When Y is a hydrogen atom, M is t-butyloxycarboryl (Boc), and X is methyl, compound Z has the following structure of formula Z-1, 35

45 [0006] The PCT patent application No. WO2009118759 disclosed a method for preparing compound Z-1, which can be summarized as follows:

[0007] Wherein 9-BBN is abbreviation for 9-Borabicyclo[3.3.1]nonane, the yield is 46% in the first step, and it’s 56% in the second step.

2 EP 3 015 456 A1

[0008] When Y is a hydrogen atom, M is t-butyloxycarbonyl (Boc), and X is tert-butyl, the said compound is represented by the following formula:

[0009] The same route for preparing the above-mentioned compound was disclosed in both Bioorganic & Medicinal Chemistry Letters,21,(12),3771-3773,2011 and PCT patent application No. WO2004039367, which can be summarized 15 as follows:

25 [0010] The yield is 41% in Bioorganic & Medicinal Chemistry Letters, 21, (12), 3771-3773, 2011, and 27% in WO2004039367. [0011] When Y is methyl, M is t-butyloxycarbonyl and X is methyl, the said compound can be represented by formula Z-3. When Y is methyl, M is t-butyloxycarbonyl (Boc) and X is a hydrogen atom, the compound has the structure of 30 formula Z-4:

[0012] PCT patent application with publication No. WO 2012068234 disclosed the following method for preparing the two aforesaid compounds on page 876.

3 EP 3 015 456 A1

[0013] The above-mentioned methods are difficult to realize commercial production due to the use of high toxicity chemical such as 9-BBN, borane and sodium cyanide etc., and difficult operation processes. Therefore, it is necessary to provide novel methods to prepare the compound of formula Z.

5 SUMMARY OF THE INVENTION

[0014] The present invention adopts the following technical solution: providing a compound having a structure of formula E,

20 wherein the position marked with * represents a chiral center, specifically, the configuration of carbon marked with * maybe R, or maybe S, or even may be the mixture of R and S. [0015] Preferably, the compound E has the following configuration,

R is R1 or R2, R1 is C1∼C6 alkyl, benzyl, p-methoxybenzyl, p-nitrobenzyl, R2 is a hydrogen atom; 35 R3 is a protecting group for carboxyl; P1 is a protecting group of nitrogen.

[0016] Specifically, R1 is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-amyl or n-hexyl; R3 is n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-amyl, n-hexyl, benzyl, triphenylmethyl, p-methoxybenzyl or p- 40 nitrobenzyl.

P1 is acetyl, trifluoroacetyl, allyloxycarbonyl, t-butyloxycarbonyl(Boc), trimethylsilyl (TMS), tert-butyldimethylsilyl (TB- DMS), benzoyl, triphenylmethyl, p-methoxybenzyl, benzyloxycarbonyl (Cbz), p-methoxybenzyloxycarbonyl (Moz), p- nitrobenzyl, m-nitrobenzyl, p-chlorobenzyl, m-chlorobenzyl, p-bromobenzyl, m-bromobenzyl or benzyl. [0017] Preferably, R 1 is C 1∼C6 alkyl; R 3 is tert-butyl, benzyl, p-methoxybenzyl or p-nitrobenzyl; P 1 is t-butyloxycarbonyl, 45 p-methoxybenzyl or carboxybenzyl.

[0018] More preferably, R1 is methyl; R3 is tert-butyl or benzyl; P1 is t-butyloxycarbonyl. Preferably, the compound E can be described by the compound of formula e1 when R is R 1:

4 EP 3 015 456 A1

wherein R1, R3 and P1 are as defined above. [0019] The compound of formula e1 is obtained from the compound of formula g and formic mixed anhydride or alkyl formate by cyclization reaction.

wherein R3, R1 and P1 are as defined above. [0020] The cyclization reaction was performed in the presence of strong base which has the ability to remove a-H. [0021] Further, the reaction yield can be improved by adding an acid. 15 [0022] The formic mixed anhydride can be selected from formic anhydride, acetic formic anhydride, formic pivalic anhydride and formic benzoic anhydride. [0023] The alkyl formate can be selected from methyl formate, ethyl formate, propyl formate and isopropyl formate. [0024] The strong base may be selected from lithium bis(trimethylsilyl)amide, lithium diisopropylamide, n-butyllithium, sodium hydride, sodium alcoholate and potassium alcoholate. The preferable sodium alcoholate may be selected from 20 sodium methoxide, sodium ethoxide and sodium isopropylate; the preferable potassium alcoholate may be potassium methoxide, potassium ethoxide, potassium isopropoxide. [0025] The acid may be trifluoroacetic acid or acetic acid. [0026] The compound g was obtained by reacting the compound of formula h with (R3CO)2 or R3X in the presence of base, 25

wherein R1, R3 and P1 is as defined above, X is a halogen atom, preferably Br or Cl. [0027] The said base may be 4-(dimethylamino)pyridine (DMAP), triethylamine, pyridine, tetramethyl guanidine, 1,8- 35 diazabicyclo[5.4.0]undec-7-ene (DBU), sodium carbonate, potassium carbonate or lithium carbonate.

[0028] The preferred solvent employed may include R 3OH, DMF, THF or acetonitrile. [0029] The compound E can be represented by formula e1 when R is R1,

wherein R1, R3 and P1 is as defined above. 50 [0030] The compound E is represented by formula e2 when R is R 2 (a hydrogen atom).

5 EP 3 015 456 A1

10 [0031] In this case, the said compound of formula e1 is hydrolyzed to generate the compound of formula e2. The preferred reaction reagent for the hydrolysis may be alkali base, such as lithium hydroxide, sodium hydroxide, potassium hydroxide and so on. [0032] In another aspect, the compound of formula E is subjected to catalytic hydrogenation to obtain the compound 15 of formula D,

wherein R5 is a hydrogen atom or C1∼C6 alkyl, the specific example is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl and n-hexyl. 30 R6 is a hydrogen atom, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl. P2 is a hydrogen atom, acetyl, trifluoroacetyl, allyloxycarbonyl, t-butyloxycarbonyl (Boc), trimethylsilyl (TMS), tert- butyldimethylsilyl (TBDMS) or benzoyl.

[0033] The catalyst for catalytic hydrogenation may be selected from palladium on carbon, platinum oxide, RaneyNi 35 as well as chiral catalyst. [0034] The said chiral catalyst maybe the compound represented by formula M1 or formula M2

wherein DTB is 50

6 EP 3 015 456 A1

X is C1~C4 alkyl. [0035] Furthermore, the compound of formula D is reduced to the compound of formula c1.

wherein R6 and P2 are as defined above. [0036] The reducing agent employed in the process above may be tributyltin hydride, triphenyltin hydride, triethyl 15 silicane, trichlorosilane, sodium borohydride, sodium trimethoxyborohydride, lithium tri-sec-butylhydridoborate, potassium Tri-Sec-Butylborohydride, lithium triethylborohydride, diisobutyl aluminium hydride (DIBAH) or sodium bis(2-methoxyethoxy)aluminiumhydride; preferably, when R 5 of compound D is a hydrogen atom, the carboxyl group can be reduced to the hydroxy group under mild reaction condition with the decrease of the formation of impurities by the activation with the addition of alkyl chloroformate such as ClCOOEt, ClCOOMe and so on to generate a mixed acid anhydride first. 20 [0037] Racemization doesn’t occur during the preparation of the compound of formula c1 from the compound of formula E according to the reduction steps described above if the compound of formula E is a single enantiomer of chiral compound, and only cis isomer of the compound of formula c1 is obtained. [0038] Furthermore, the compound of formula c1 can convert to the compound of formula b1 by removal of the carboxyl group. 25

wherein P1 and P2 are as defined above. [0039] The reagent employed in the process of removing the carboxyl group may be selected from formic acid, trifluoroacetic acid, hydrochloric acid, acetic acid and p-toluenesulfonic acid, etc. [0040] The compound of formula b1 is subjected to alkylation to produce the compound of formula A1, 40

wherein R4 is C1~C6 alkyl. [0041] Alkylating reagent may be selected from iodomethane, bromoethane, dimethyl sulfate, diethyl sulfate, methyl methanesulfonate, methyl p-toluenesulfonate, methyl trifluoromethansulfonate, oxalic acid dimethyl ester and methyl carboxylate etc. 55 [0042] In order to improve the nucleophilicity of the hydroxy group of compound b1 or b2, the hydroxyl group may be activated with strong base such as metallic sodium, sodium hydride, n-butyllithium and so on to form the corresponding sodium alkoxide or lithium alkoxid, which reacts with alkylating reagent in the presence of phase transfer catalyst, for example, quaternary ammonium salt, polyethylene glycol and etc.

7 EP 3 015 456 A1

[0043] The compound of formula c1 is converted to the compound of formula A1 without racemization after the steps of removal the protecting group of carboxyl group and alkylation if it is a single enantiomer of chiral compound. [0044] Alternatively, the compound of formula c1 can be converted to the compound of formula A1 directly by alkylation process. 5 [0045] The compound c1 is alkylated directly to give the compound A1 which will be racemizated if the carboxyl group in 2-position of compound c1 is a single chiral. [0046] The present invention provides the preparation method for pyrrolidine-2-carboxylic acid derivatives and has advantages that the compound of formula D is obtained as cis isomer by the catalytic hydrogenation of double bond in the compound of formula E when the compound E is a single enantiomer of chiral compound. But in general, a person 10 skilled in the art knows that the product is a racemic mixture when the double bond of alkene is subjected to catalytic hydrogenation. For example, the compound of formula N which has a similar structure as the compound provided by the present invention undergoes catalytic hydrogenation to produce a product with racemization at 4 position (see comparison example 1). This has not been clearly indicated in common knowledge. Therefore, the compound E provided by the present invention has achieved an unexpected technical effect. 15

[0047] The method also has the advantages of cheap raw materials, simple operation, mild conditions, and effectively decreases the production cost. 30 DETAILED EMBODIMENTS

Example 1: The preparation of 1-tert-butyl-5-methyl-2-((tert-butyloxycarbonyl) amino) pentanedioate

35 [0048]

[0049] To a 100 ml one-necked flask was added 5-methyl-2-((tert-butyloxycarbonyl) amino)-pentanedioate (7.8g, 24.6mmol), di-tert-butyl dicarbonate (5.9g, 27mmol), 4-dimethylaminopyridine (0.9g, 7.38mmol) and 30 ml tertiary bu- 45 tanol. After the mixture was stirred at 25°C overnight, the solvent was evaporated and the residue was purified by column chromatography to afford 7.17 g 1-tert-butyl-5-methyl-2-((tert-butyloxycarbonyl)amino) pentanedioate as white solid with a yield of 91.9%.

Example 2: The preparation of 1-benzyl-5-methyl-2-((tert-butyloxycarbonyl) amino) pentanedioate 50 [0050]

8 EP 3 015 456 A1

[0051] To a 100 ml one-necked flask was added 5-methyl-2-((tert-butyloxycarbonyl) amino)-pentanedioate (7.8g, 24.6mmol), di-benzyl dicarbonate (6.86g, 27mmol), triethylamine (0.75g, 7.4mmol) and 30 ml methanol. After the mixture was stirred at 30°C for one night, the solvent was evaporated and the residue was purified by column chromatography to afford 7.1 g 1-benzyl-5-methyl-2-((tert-butyloxycarbonyl) amino) pentanedioate as white solid with a yield of 82.3%. 5 Example 3: The preparation of 1-tert-butyl -5-methyl-2-acetamino pentanedioate

[0052]

15 [0053] The procedure of example 1 was repeated by using 5g 5-methyl-2-acetamino pentanedioate as starting material to obtain 5.5 g 1-tert-butyl -5-methyl-2-acetamino pentanedioate with a yield of 86.6%.

Example 4: The preparation of (S)-1-tert-butyl -5-methyl-2-benzyloxycarbonylamino pentanedioate 20 [0054]

[0055] The procedure of example 1 was repeated by using 2.95 g 5-methyl-2-benzyloxycarbonylamino pentanedioate 30 as starting material to obtain 3.5g with a yield of 99%.

Example 5: The preparation of N- t-butyloxycarbonyl-2-t-butyloxycarbonyl-4-methoxycarbonyl-2,3-dihydro- 1H-pyrrole

35 [0056]

45 [0057] 60 ml lithium bis(trimethylsilyl)amide (7.6g, 45.4mmol) was charged into a 250 ml three-necked flask under the protection of nitrogen and cooled to -78°C. A solution of 1-t-butyl-5-methyl-2-((t-butyloxycarbonyl) amino) pentanedioate (8.0g, 25.2mmol) in 20ml THF was added dropwise. After the addition, the mixture was maintained at -78°C for 1h. A solution of acetic formic anhydride (2M, 40mmol) in 20 ml THF was added dropwise slowly. The inner temperature was 50 maintained below -70°C. After the addition, the mixture was maintained at -78°C for 3h, then heated to 5°C. The resulting mixture was quenched with 4.0ml of acetic acid and 30ml of water, extracted with ethyl acetate and the combined organic phase was dried over MgSO4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25°C, concentrated and purified by column chromatography to afford 6.8g N-t-butyloxycarbonyl-2-t-butyloxy- 55 carbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrrole as white solid with a yield of 82.9%. 1 [0058] HNMR (400Mz, CDCl3): δ=1.48-1.49 (m, 18H), δ=2.80-2.87 (m, 1H), δ=3.15-3.28 (m, 1H), δ=4.56-4.67 (m, 1H), δ=7.42-7.58 (d, 1H).

9 EP 3 015 456 A1

Example 6: The preparation of N-benzyloxycarbonyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro- 1H-pyrrole

[0059] 5

15 [0060] To a 250ml of three-necked bottle was added 60ml of LHMDS (7.6g, 45.4mmol) with the protection of nitrogen, then cooled to -78°C, after the addition of a solution of 1-tert-butyl 5-methyl 2-((tert-butoxycarbonyl)amino)pentanedioate (8.8g, 27.8mmol) in 20 ml THF, the mixture was stirred for another 1 hour at -78°C, then a solution of acetic formic anhydride in 20ml of THF was added dropwise to maintain the inner temperature below -70°C. After addition, the mixture 20 was stirred for another 3 hours at -78°C, the reaction solution was warmed to 5°C, then quenched the reaction with 4.0ml of acetic acid and 30ml of water, extracted with ethyl acetate and combined the organic phase then dried over

MgSO4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25°C, after the addition of 40 ml water, then concentrated, and extracted with DCM (50ml 3 3), combined the organic phase and 25 evaporated to dryness to give 8.7 g of N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro- 1H-pyrrole in 95.7% yield.

Example 7: The preparation of (S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl -2,3-dihydro-1H-pyrrole

30 [0061]

40 [0062] To a 250ml of three-necked bottle was added a solution of 25mln BuLi in hexane(1.6M, 40mmol) under the protection of nitrogen, then cooled to -78°C, after the addition of the solution of S( )-1-tert-butyl-5-methyl-2-acetamino pentanedioate (6.5g, 25.1mmol) in 20 ml THF, the mixture was stirred for another 1 hour at -78°C, then a solution of formic pivalic anhydride in 20ml of THF (2M, 40mmol) was added dropwise slowly to maintain the inner temperature 45 below -70°C, after the addition, stirred at -78 °C for 3 hours, and warmed to 5°C, then quenched with 4.0ml of acetic

acid and 30ml of water, extracted with ethyl acetate. The combined organic phase was dried over MgSO 4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25°C, then concentrated, and then purified by column chromatography to give 5.7 g of ( S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl -2,3-dihydro- 50 1H-pyrrole in 84.4% yield.

Example 7-2: The preparation of ( S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl -2,3-dihydro-1H-pyrrole

[0063] 55

10 EP 3 015 456 A1

10 [0064] To a 250ml of three-necked bottle was added a solution of 25mln BuLi in hexane(1.6M, 40mmol) under the protection of nitrogen, then cooled to -78°C, after the addition of the solution of S( )-1-tert-butyl-5-methyl-2-acetamino pentanedioate (6.5g, 25.1mmol) in 20 ml THF, the mixture was stirred for another 1 hour at -78°C, then a solution of formic pivalic anhydride in 20ml of THF (2M, 40mmol) was added dropwise slowly to maintain the inner temperature below -70°C, after the addition, stirred at -78°C for 3 hours, and warmed to 5°C, then quenched with 4.0ml of acetic acid 15 and 30ml of water, extracted with ethyl acetate. The combined organic phase was dried over MgSO4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25°C, then concentrated, after the addition of 40 ml water, extracted with DCM (3X50ml), ), then purified by column chromatography to give 6.1 g of ( S)-N- acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl -2,3-dihydro-1H-pyrrole in 90.5% yield. 20 Example 8: The preparation of (R)-N-trimethylsilyl -2-tert-butoxycarbonyl-4-isopropoxycarbonyl-2,3-dihydro- 1H-pyrrole

[0065] 25

35 [0066] To a 250ml of three-necked bottle was added LDA (3.0g, 28mmol) with the protection of nitrogen, then cooled to -78°C, after the addition of (R)-1-tert-butyl-5-isopropyl 2-((trimethylsilyl)amino)pentanedioate (4.8g, 15.1mmol) (prepared according to Example 1) in 15ml of THF, the mixture was stirred for another 1.5 hours at -78°C, then a solution of formic acetic anhydride in 12ml of THF(2M, 24mmol) was added dropwise slowly to maintain the inner temperature 40 below -70°C, after addition, stirred for another 4 hours at -78°C, the reaction solution was warmed to 5°C, then quenched the reaction with 3.0ml of acetic acid and 20ml of water, extracted with ethyl acetate and the combined organic phase

was dried over MgSO 4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25°C, then concentrated, purified by column chromatography to give 3.74g of ( R)-N- trimethylsilyl -2-tert-butoxycarbonyl- 45 4-isopropoxycarbonyl-2,3-dihydro-1H-pyrrole in 75.6% yield.

Example 9: The preparation of ( S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-carboxyl -2,3-dihydro-1H-pyrrole

50 [0067]

11 EP 3 015 456 A1

10 [0068] To a 100ml of single-necked bottle was added (S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrrole (3.2g, 10mmol) (prepared by the method of Example 5), LiOH (0.63g, 15mmol), 15ml of water and 15ml of THF, then the mixture was stirred at 25°C overnight, extracted with ethyl acetate to remove the organic impurities, the aqueous phase was adjust to PH=3, then extracted with ethyl acetate 3(315ml), dried over MgSO4, filtrated and evaporated to afford 3.1g ofS )-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-carboxyl ( -2,3-dihydro- 15 1H-pyrrole in 100% yield. 1 [0069] HNMR (400Mz, CDCl3): δ=1.49-1.53 (m, 18H), δ=2.83-2.86 (m, 1H), δ=3.16-3.29 (m, 1H), δ=4.59-4.70 (m, 1H), δ=7.54-7.72 (d, 1H).

Example 10: The preparation of (2 S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbony-4-methoxycarbonyl pyrro- 20 lidine

[0070]

[0071] To a 100ml of single-necked bottle was added ( S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxycar- 35 bonyl-2,3-dihydro-1H-pyrrole (3.27g, 10mmol) (prepared by the method of Example 5), 10% wet Pd/C (0.7g, 30%), one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 3.3g of (2S ,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbony-4-methoxycarbonyl pyrrolidine was obtained in 100% yield, ee 99%. 1 [0072] HNMR (400Mz, CDCl3): δ=1.42-1.45 (m, 18H), δ=2.26-2.34 (m, 1H), δ=2.46-2.51 (m, 1H), δ=3.00-3.07 (m, 40 1H), δ=3.69 (s, 3H), δ=3.69 - 3.86 (m, 1H), δ=4.12-4.20 (m, 1H).

Example 11: The preparation of (2S,4S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine

[0073] 45

55 [0074] To a 100ml of single-necked bottle was added (S)-N- acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3- dihydro-1H-pyrrole (2.7g, 10mmol), 10% wet Pd/C (0.7g, 30%), one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 2.7g of ( 2S,4S)-N-acetyl-2-tert-butoxycarbonyl-4-

12 EP 3 015 456 A1

methoxycarbonyl pyrrolidine was obtained in 100% yield, ee 97.5%.

Example 11-2: The preparation of (2S, 4S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine

5 [0075]

[0076] To a 100ml of single-necked bottle was added (S)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrrole (2.7g, 10mmol), 0.3g of Raney nickel, one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 2.7g of (2S,4S)-N-acetyl-2-tert-butoxycarbonyl-4-methox- 20 ycarbonyl pyrrolidine as colourless oil was obtained in 100% yield, ee 97.6%.

Example 12: The preparation of (2R,4R)-N-(trimethylsilyl)-2,4-di(tert-butoxycarbonyl) pyrrolidine

[0077] 25

35 [0078] To a 100ml of single-necked bottle was added R()-N-(trimethylsilyl)-2,4-di(tert-butoxycarbonyl)-2,3-dihydro- 1H-pyrrole (3.4g, 10mmol), 10% wet Pd/C(0.7g, 30%) and 5ml of methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 3.4g of (2R,4R)-N-(trimethylsilyl)-2,4-di(tert-butoxycarbonyl)pyrrolidine as colourless oil was obtained in 99% yield, ee 98%. 40 Example 13: the preparation of (2S,4S)-2-carboxyl-4-(ethoxycarbonyl) pyrrolidine

[0079]

[0080] To a 100ml of single-necked bottle was added (S)-N- benzyloxycarbonyl-2-benzyloxycarbonyl-4-ethoxycarb- 55 onyl-2,3-dihydro-1H-pyrrole (4.0g, 10mmol) (obtained according the example 5), 10% wet Pd/C (0.7g, 30%), one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C overnight after filtration and evaporation, 4 g of (2S,4S)-2-carboxyl-4-(ethoxycarbonyl) pyrrolidine was obtained in 100% yield, ee 98.7%.

13 EP 3 015 456 A1

Example 14: The preparation of (S)-N-tert-butoxycarbonyl-2-benzyloxycarbonyl-4-ethoxycarbonyl-2,3-dihydro- 1H-pyrrole

[0081] 5

15 [0082] To a 250ml of three-necked bottle was addedt BuONa (3.8g, 40 mmol) with the protection of nitrogen, then cooled to -70°C, after the addition a solution of (S)-1-benzyl-5-ethyl 2-((tert-butoxycarbonyl)amino)pentanedioate (9.2g, 25.1mmol) in 20m THF, the mixture was stirred for another 3 hour at -70°C, then a solution of propylformate in 20ml of THF (2M, 40mmol) was added dropwise slowly to maintain the inner temperature below -70°C, after addition and main- 20 tained at -70°C for another 5 hours. The reaction solution was warmed to 5°C, then quenched the reaction with 4.0ml

of acetic acid and 30ml of water, extracted with ethyl acetate, dried over MgSO 4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride, cooled to 5°C, after the addition of TFA (3.16g, 27.7mmol), the mixture was warmed to for 25°C with stirring for 4 hours, then concentrated, after40 ml of water was added and extracted with DCM (50ml 3 3) to give 9 g of N-tert-butoxycarbonyl-2-benzyloxycarbonyl- 4-ethoxycar- 25 bonyl-2,3-dihydro-1H-pyrrole in 95.7% yield. ee 98.3%.

Example 15: the preparation of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl -4-carboxyl pyrrolidine

[0083] 30

40 [0084] To a 100ml of single-necked bottle was added S()-N-tert-butoxycarbonyl-2-tert -butoxycarbonyl-4-carboxyl- 2,3-dihydro-1H-pyrrole (3.13g, 10mmol), 10% wet Pd/C(0.7g, 30%), one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 3.15g of ( 2S,4S)-N-tert-butoxycarbonyl-2-tert- butoxycarbonyl-4-carboxyl pyrrolidine was obtained in 100% yield, ee 98.8%. 1 [0085] HNMR (400Mz, CDCl3): δ=1.45-1.47 (m, 18H), δ=2.32-2.39 (m, 1H), δ=2.49-2.55 (m, 1H), δ=3.06-3.13 (m, 45 1H), δ=3.72-3.89 (m, 2H), δ=4.16-4.25 (m, 1H).

Example 16: the preparation of (2R,4R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine

[0086] 50

14 EP 3 015 456 A1

10 [0087] To a 100ml of single-necked bottle was added (R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrrole (2.7g, 10mmol), 10% wet Pd/C(0.7g, 30%), 5ml of Methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 2.7g of ( 2R,4R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine as colorless oil was obtained in 100% yield, ee 97.5%. 15 Example 16-2: The preparation of (2R,4R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine

[0088]

30 [0089] To a 100ml of single-necked bottle was added (R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrrole (2.7g, 10mmol), 0.3g of Raney nickel, 5ml of Methanol, then the mixture was stirred at 25°C overnight, after filtration and evaporation, 2.7g of (2R,4R)-N-acetyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine was obtained in 100% yield, ee 97.5%.

35 Example 17: The preparation of ( 2S,4S)-N-tert-butoxycarbonyl-2-(p-methoxybenyloxy)carbonyl-4-hydroxyethyl pyrrole

[0090]

55 [0091] To a mixture of 2S,4S ( )-N-tert-butoxycarbonyl-2-(p-methoxybenyloxy)carbonyl-4-propoxy pyrrolidine (3g, 8.26mmol) in 20ml of methanol was added diisobutyl aluminium hydride(3.55g, 25mmol), then the mixture was stirred at 25°C overnight, quenched by dilute HCl, extracted with ethyl acetate, then purified by column chromatography to give 2.45g of 2S,4S ( )-N-tert-butoxycarbonyl-2-(p-methoxybenyloxy)carbonyl-4-hydroxyethyl pyrrole in 81.2% yield, ee

15 EP 3 015 456 A1

96.8%.

Example 18: The preparation of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl -4-hydroxyethyl pyrrolidine 5 [0092]

[0093] To a mixture of2S,4S ( )-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine (2g, 6.1mmol) in 20ml of isopropanol was added sodium borohydride (0.74g, 20mmol), then the mixture was stirred at 25°C overnight, quenched by dilute HCl, extracted with ethyl acetate, then purified by column chromatography to give 1.5g 20 of (2S,4S)-N-tert-butoxycarbonyl-2- tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine as oil in 81.9% yield, ee 81.9%.

Example 18-2: The preparation of (2S,4S)- N-tert-butoxycarbonyl-2-tert-butoxycarbonyl -4-hydroxyethyl pyrrolidine

25 [0094]

35 [0095] To a mixture of2S,4S ( )-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine (2g, 6.1mmol) in 20ml of isopropanol was added NaBH4 (0.74g, 20mmol), then the mixture was stirred at 25°C overnight, quenched by dilute HCl, extracted with ethyl acetate, then combined and concentrated the organic phase which was further purified via recrystallization by ethanol to give 1.7g of (2S,4S)- N-tert-butoxycarbonyl-2- tert-butoxycarbonyl-4- 40 hydroxyethyl pyrrolidine as white solid in 93.2% yield, ee 98.4%.

Example 19: The preparation of (2R,4R)-N-trimethylsilyl -2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine

[0096] 45

55 [0097] To a mixture of (2R,4R)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine (2.5g, 7.3mmol) in 20ml of THF was added red aluminum (4.04g, 20mmol), then the mixture was stirred at 25°C overnight, quenched by dilute HCl, extracted with ethyl acetate, then the combined organic phase was concentrated, and then purified by column chromatography to give 1.59g of 2R,4R( )-N-trimethylsilyl -2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine in 79.9%

16 EP 3 015 456 A1

yield.

Example 19-2: The preparation of (2R,4R)-N-trimethylsilyl -2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine

5 [0098]

15 [0099] To a mixture of (2R,4R)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-methoxycarbonyl pyrrolidine (2.5g, 7.3mmol) in 20ml ofTHF was added red aluminum (4.04g, 20mmol), then the mixture was stirred at 25°C overnight, quenched by dilute HCl, extracted with ethyl acetate, then combined and concentrated the organic phase which was recrystallized by ethanol to give 1.82g of 2R,4R( )-N-trimethylsilyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine in 91.1% yield, ee 20 97.9%.

Example20: The preparation of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine

[0100] 25

35 [0101] To a 100ml of single-necked flask was added ( 2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-carboxyl pyrrolidine (0.66g, 2.11mmol), TEA (0.4ml, 2.74mmol) and 5ml of methylene chloride, then ethyl chloroformate (252mg, 2.32mmol) was added dropwise, after stirring for another 1hour at 25°C, washed with water and organic phase was concentrated, then the residue was dissolved in THF and water, NaBH4 (230mg, 6mmol) was added, after stirring for another 3 hours at 25°C, quenched by dilute HCl, and extracted with ethyl acetate, dried over MgSO 4, then filtered and 40 evaporated to give 540mg of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine as colorless oil in 85.2% yield.

Example 20-2: The preparation of N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine

45 [0102]

55 [0103] To a 100ml of single-necked flask was added ( 2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-carboxyl pyrrolidine (0.66g, 2.11mmol), TEA (0.4ml, 2.74mmol) and 5ml of methylene chloride, then ethyl chloroformate (252mg, 2.32mmol) was added dropwise, after stirring for another 1hour at 25°C, washed with water and organic phase was

17 EP 3 015 456 A1

concentrated, then the residue was dissolved in THF and water, NaBH4 (230mg, 6mmol) was added, after stirring for another 3 hours at 25°C, quenched by dilute HCl, and extracted with ethyl acetate, dried over MgSO4, then filtered, evaporated and recrystallized with ethanol to give 566mg of N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine as colorless oil in 89.2%" ee 97.6%. 5 Example 21: The preparation of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl-2,3-dihydro-1H-pyrrole

[0104] 10

20 [0105] To a mixture of (2S,4S)-N-tert-butoxycarbonyl-2--tert-butoxycarbonyl-4-methoxycarbonyl 2,3-dihydro-1H-pyrrole (3g, 9.2mmol) dissolved in 20ml of THF, diisobutyl aluminium hydride(5.6g, 46mmol) was added, after stirred overnight at 25 °C, quenched by dilute HCl, and extracted with ethyl acetate, concentrated, then recrystallized by ethanol to give 2.52g of 2S,4S( )-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl-2,3-dihydro-1H-pyrrole in 91.7% yield. 25 Example 22: the preparation of (2R,4R)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-hydroxyethyl-2,3-dihydro-1H- pyrrole

[0106] 30

40 [0107] To a mixture of (2R,4R)-N-trimethylsilyl-2,4-di(tert-butoxycarbonyl)-2,3-dihydro-1H-pyrrole (1.9g, 5.9mmol) in 20ml of THF, red aluminum (5.7g, 28mmol) was added, after stirring overnight at 25°C, quenched by dilute HCl, and extracted with ethyl acetate, then purified by column chromatography to give 1.08g of (2R,4R)-N-trimethylsilyl-2-tert- butoxycarbonyl-4-hydroxyethyl- 2,3-dihydro-1H-pyrrole as oil in 67.5% yield. 45 Example 23: the preparation of (2S,4S)-N-tert-butoxycarbonyl-2-carboxyl-4-hydroxyethyl pyrrolidine

[0108]

18 EP 3 015 456 A1

[0109] (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine (3g, 10mmol) was dissolved in 20ml of hydrochloride ethanol solution. After stirring for 3 hours at 25°C, the solvent was evaporated, then 15% NaOH and (Boc) 2O(3.27g, 1.5eq) were added, stirred for 3 hours, and extracted with ethyl acetate, then adjusted to PH=2, extracted with ethyl acetate again, concentrated to give 2.2g of white solid in 89.7% yield. 5 Example 24: the preparation of (2R,4R)-2-carboxyl-4-hydroxyethyl pyrrolidine

[0110]

[0111] (2R,4R)-N-trimethylsilylamino-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine (2.7g, 10mmol) was dissolved 20 in 20ml of hydrochloride ethanol solution. After stirring for 3 hours at 25°C, the solvent was evaporated to give 1.2g of (2R,4R)-2-carboxyl-4- hydroxyethyl pyrrolidine in 82.7% yield.

Example 25: the preparation of (2S,4S)-N-tert-butoxycarbonyl-2-carboxyl-4-methoxyethyl pyrrolidine

25 [0112]

35 [0113] (2S,4S)-N-tert-butoxycarbonyl-2-carboxyl-4-hydroxyethyl pyrrolidine (2.45g, 10mmol) was dissolved in 50% of NaOH, then methyl iodide (4.26g, 0mmol) was added, after stirring for 3 hours at 2 °C, the resulting mixture was extracted with ethyl acetate, then adjusted to PH=2, extracted with ethyl acetate, the organic phase was washed with water, dried over MgSO4, concentrated to give 2.5g of white solid in 96.5% yield.

40 Example 26: the preparation of (2 S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxyethylpyrrolidine

[0114]

[0115] (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine (3.0g, 10mmol) was dissolved in 50% of NaOH, then methyl iodide (4.26g, 0mmol) was added. After stirring for 3 hours at 25 °C, the resulting mixture 55 was extracted with ethyl acetate, then adjusted to PH=2, extracted with ethyl acetate, and the organic phase was washed

with water, dried over MgSO4, and concentrated to give 2.5g of white solid in 96.5% yield.

19 EP 3 015 456 A1

Example 26-2: the preparation of ( 2S,4S)- N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-methoxyethyl pyrrolidine

[0116] 5

15 [0117] To a mixture of ( 2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine (3.0g, 10mmol)

in ethyl acetate, Bu4NBr (0.65g, 2mmol) and methyl sulphate (2.5g, 20mmol) were added, after dissolving completely, 2g of NaOH solution (40%) was added dropwise with maintaining the inner temperature at -5 °C to 5 °C. After the addition, the mixture was maintained at this temperature for 3 hours, and extracted with ethyl acetate, and then the organic phase was washed with dilute HCl aqueous solution and dilute NaOH aqueous solution respectively. The organic solvent was 20 concentrated then recrystallized by hexane to give 2.47g of white solid in 95.2% yield.

Example 27: the preparation of (2S,4S)-2,4-dicarboxyl pyrrolidine

[0118] 25

40 [0119] Chiral catalyst M (7.0mg, 0.007mmol), EtONa (38mg, 0.71mmol) and S()-N-p-methoxybenzyl-2-tert-butoxycarbonyl-4-benzyloxycarbonyl-2,3-dihydro-1H-pyrrole (3g, 7.1mmol) were weighted into a reaction inner tube under the protection of N2 atmosphere, then 15ml of ethanol and 3ml of DMF were added. The reaction tube was placed into an autoclave. The original atmosphere was displaced with hydrogen atmosphere. The hydrogen pressure inside the auto- 45 clave was ultimately maintained at 1.4-1.5 MPa and then heated to 50°C in an oil bath with reacting for 3h. Starting material was consumed completely until the inside pressure did not continue to decrease, then the reaction was stopped and the resulting mixture was concentrated. 30ml of water and 30ml of ethyl acetate were added, and aqueous phase was extracted with ethyl acetate (2320ml). the combined organic phase was washed with saturated brine, dried over MgSO4, filtered and concentrated to give 1.0g of 2S,4S( )-2,4-dicarboxyl pyrrolidine in 88.6% yield. The product was 50 analyzed by chiral HPLC, the chiral purity is 97.5% ee.

Example 28: the preparation of (S)-1-benzyl-5-methyl-2-((tert-butoxycarbonyl)amino)pentanedioate

[0120] 55

20 EP 3 015 456 A1

[0121] Toa 100ml of single-neckedbottle was added ( S)-5-methyl-2-((tert-butoxycarbonyl)amino) pentanedioate (7.8g, 24.6mmol), benzyl chloride(3.4g, 27mmol), K2CO3(3.1g, 29.5mmol) and 30ml of DMF, the mixture was maintained at 40 to 60 °C for 6 hours, after the completion of the reaction, the solvent was evaporated, extracted with methyl tert-butyl 10 ether after the addition of water, and then the organic phase was evaporated to dryness to give 8.45g of (S)-1-benzyl- 5-methyl-2-((tert-butoxycarbonyl)amino)pentanedioate as light yellow oil in 97.9% yield.

Example 29: the preparation of (S)-N-tert-butoxycarbonyl-2-benzyloxycarbonyl-4-methoxycarbonyl-2,3-dihydro-1H-pyrro le 15 [0122]

25 [0123] To a 250ml of three-necked bottle was added 60ml of LHMDS (7.6g, 45.4mmol) under the protection of nitrogen, then cooled to -70°C to -78°C, after the addition of (S)1-tert-butyl-5-methyl-2- (tert-butoxycarbonyl)amino pentanedioate (8.0g, 25.2mmol) in 40ml of THF, the mixture was maintained at this temperature for 1 hour, then ethyl formate (4.4g, 60mmol) was added dropwise slowly and the inner temperature was maintained below -70°C. After the addition, the 30 mixture was maintained at this temperature for 8 hours. After the completion of the reaction, the reaction solution was warmed to about -40°C, 3.5ml of acetic acid was added, and then quenched with 30ml of water, extracted with ethyl acetate, dried over MgSO 4, filtered and concentrated to give a light yellow oil. Then the above mentioned oil was dissolved in methylene chloride. After the addition of TFA (3.16g, 27.7mmol), the mixture was stirred for 4 hours at 25 °C, then concentrated to dryness to give 8.8 g of ( S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl -4-methoxycarbonyl-2,3-dihy- 35 dro-1H-pyrrole in 96.7% yield.

Example 30: the preparation of (2S,4S)-2-carboxyl-4-methoxycarbonyl pyrrolidine

[0124] 40

[0125] To a 100ml of single-necked bottle was added ( S)-N-tert-butoxycarbonyl-2-benzyloxycarbonyl-4-methoxycar- 50 bonyl-2,3-dihydro-1H-pyrrole (3.0g, 8.3mmol) (prepared by the method of Example 5), 10% wet Pd/C(0.7g, 30%), one drop of acetic acid and 5ml of Methanol, then the mixture was stirred at 25 °C overnight, after filtration and evaporation, 2.27g of (2S,4S)-2-carboxyl-4-methoxycarbonyl pyrrolidine as colorless oil was obtained in 100% yield, ee 98.8%.

Example 31: the preparation of (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine 55 [0126]

21 EP 3 015 456 A1

10 [0127] The procedure of example 15 was repeated to afford (2S,4S)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4- hydroxyethyl pyrrolidine containing (2S,4R)-N-tert-butoxycarbonyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine, ee 61.1%%.

Example 32: the preparation of (2R,4R)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine 15 [0128]

[0129] The procedure of example 15 was repeated to afford (2R,4R)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine containing (2R,4S)-N-trimethylsilyl-2-tert-butoxycarbonyl-4-hydroxyethyl pyrrolidine, ee 55.4%.

30 Comparison Example 1: the preparation of (2S)-2,4-dimethoxycarbonyl pyrrolidine

[0130]

[0131] To a 100ml of single-necked bottle was added (S)-2,4-dimethoxycarbonyl-2,3-dihydro-1H-pyrrole (1.85g, 10mmol), 10% wet Pd/C(0.7g, 30%), one drop of acetic acid and 5ml of methanol, then the mixture was stirred at 25°C 45 overnight, after filtration and evaporation, 1.80g of (2 S)-2,4-dimethoxycarbonyl pyrrolidine as colorless oil was obtained in 96.2% yield. [0132] Thus it can be seen from the comparison example that, the product (2S)-2,4-dimethoxycarbonyl pyrrolidine is racemic at 4 position.

[0133] The experimental results presented below are got in accordance with example 6 when R 1, R3, P1 are different 50 substituents.

22 EP 3 015 456 A1

Product R1 R3 P1 Yield e1-1 methyl t-Bu trifluoroacetyl 73.2% e1-2 methyl t-Bu allyloxycarbonyl 77.0% 15 e1-3 methyl t-Bu triphenylmethyl 80.4% e1-4 methyl t-Bu benzyl 85.7% e1-5 methyl t-Bu Cbz 90.1% e1-6 methyl t-Bu p-chlorobenzyl 87.6% e1-7 isopropyl t-Bu Boc 85.1% 20 e1-8 isopropyl t-Bu Cbz 84.2% e1-9 isopropyl t-Bu benzyl 82.2% e1-10 n-hexyl t-Bu Boc 61.3% e1-11 methyl benzyl benzyl 86.7% 25 e1-12 methyl benzyl p-chlorobenzyl 88.9% e1-13 methyl benzyl Cbz 94.3% e1-14 isopropyl benzyl Boc 74.7% e1-15 methyl isopropyl Boc 78.7% e1-16 methyl n-hexyl Boc 70.0% 30 e1-17 methyl p-nitrobenzyl Boc 83.5% e1-18 methyl ethyl Boc 86.9% e1-19 benzyl t-Bu Boc 88.8%

35 [0134] The experimental results presented below are got in accordance with example 6 in the presence of different reaction reagents.

Product R3 base formic mixed anhydride / alkyl formate Yield e1-20 t-Bu lithium bis(trimethylsilyl)amide formic anhydride 85.3%

50 t-Bu lithium bis(trimethylsilyl)amide pivalic formic anhydride 78.0% t-Bu lithium bis(trimethylsilyl)amide benzoic formic anhydride 73.5% t-Bu lithium diisopropylamide formic anhydride 79.1% t-Bu lithium diisopropylamide acetic formic anhydride 86.7% t-Bu lithium diisopropylamide pivalic formic anhydride 71.9% 55 t-Bu sodium ethoxide acetic formic anhydride 86.9% t-Bu sodium propoxide acetic formic anhydride 87.2% t-Bu lithium bis(trimethylsilyl)amide ethyl formate 94.8%

23 EP 3 015 456 A1

(continued)

Product R3 base formic mixed anhydride / alkyl formate Yield t-Bu sodium methoxide pivalic formic 67.2% 5 t-Bu sodium methoxide anhydride n-propylformate 65.9% e1-21 benzyl lithium bis(trimethylsilyl)amide formic anhydride 82.5% benzyl lithium bis(trimethylsilyl)amide pivalic formic anhydride 78.7% benzyl lithium bis(trimethylsilyl)amide benzoic formic anhydride 70.3% 10 benzyl lithium bis(trimethylsilyl)amide acetic formic anhydride 96.6% benzyl lithium bis(trimethylsilyl)amide methyl formate 84.5% benzyl lithium bis(trimethylsilyl)amide n-propylformate 85.7% benzyl n-butyllithium acetic formic anhydride 89.1%

15 benzyl n-butyllithium ethyl formate 87.4% benzyl sodium methoxide acetic formic anhydride 90.9% benzyl sodium methoxide ethyl formate 89.7% benzyl sodium methoxide methyl formate 70.4% benzyl potassium isopropoxide benzoic formic anhydride 63.0% 20 benzyl potassium isopropoxide n-propylformate 68.1% benzyl sodium hydride ethyl formate 79.8% benzyl sodium hydride methyl formate 63.6% benzyl sodium isopropoxide pivalic formic anhydride 70.2%

25 [0135] The experimental results presented below are got in accordance with example 10 when R 5, R6, P2 are different substituents.

Substrate Product R5 R6 P2 Yield ee (4S) 40 e1-1 D-1 methyl t-Bu trifluoroacetyl 97.8% 97.2% e1-2 D-2 methyl t-Bu allyloxycarbonyl 60.1% 95.7% e1-3 D-3 methyl t-Bu H 83.6% 96.2% e1-4 D-4 methyl t-Bu H 100% 97.6% 45 e1-5 D-5 methyl t-Bu Cbz 100% 97.7% e1-6 D-6 methyl t-Bu H 100% 98.8% e1-7 D-7 isopropyl t-Bu Boc 100% 91.9% e1-8 D-8 isopropyl t-Bu Cbz 100% 91.2% e1-9 D-9 isopropyl t-Bu H 100% 89.7% 50 e1-10 D-10 n-hexyl t-Bu Boc 100% 78.7% e1-11 D-11 methyl H H 100% 96.8% e1-12 D-12 methyl H H 98.8% 96.9% e1-13 D-13 methyl H Cbz 100% 97.9%

55 e1-14 D-14 isopropyl H Boc 100% 89.1% e1-15 D-15 methyl isopropyl Boc 100% 80.3% e1-16 D-16 methyl n-hexyl Boc 100% 89.7%

24 EP 3 015 456 A1

(continued)

Substrate Product R5 R6 P2 Yield ee (4S) e1-17 D-17 methyl H Boc 99.0% 98.2% 5 e1-18 D-18 methyl ethyl Boc 100% 65.3% e1-19 D-19 H t-Bu Boc 100% 56.9%

Claims 10 1. A compound of formula E,

wherein R is R1 or R2, R1 is C1∼C6 alkyl, benzyl, p-methoxybenzyl or p-nitrobenzyl, R 2 is a hydrogen atom; R3 is a protecting group for carboxyl; 25 P1 is a protecting group of nitrogen.

2. The compound according to claim 1, wherein R1 is C1∼C6 alkyl, R3 is tert-butyl, benzyl, p-methoxybenzyl or p- nitrobenzyl; P1 is t-butyloxycarbonyl, p-methoxybenzyl or benzyloxycarbonyl.

30 3. The compound according to claim 2, wherein R 1 is methyl, R3 is tert-butyl or benzyl, P1 is t-butyloxycarbonyl.

4. A method for preparing the compound of formula (e1), comprising subjecting the compound of formula (g) to a cyclization reaction,

45 wherein R1, R3 and P1 are as defined in claim 1.

5. The method according to claim 4, wherein the reagents employed in the process of cyclization reaction are a base/ a formic mixed anhydride, or an alkyl formate/ an acid; wherein the base is selected from lithium bis(trimethylsilyl)amide, lithium diisopropylamide, n-butyllithium, sodium alcoholate and potassium alcoholate; wherein the formic 50 mixed anhydride is selected from acetic formic anhydride, formic pivalic anhydride and formic benzoic anhydride; wherein the acid is selected from trifluoroacetic acid and acetic acid, and wherein the alkyl formate is selected from methyl formate, ethyl formate, propyl formate.

6. The method according to claim 5, wherein the base is lithium bis(trimethylsilyl)amide. 55 7. The method according to claim 5, wherein the formic mixed anhydride is acetic formic anhydride; the alkyl formate is ethyl formate.

25 EP 3 015 456 A1

8. The method according to claim 4, further comprising the step of reacting the compound of formula (h) with (R 3CO)2 or R3X in the presence of a base to afford the compound of formula (g),

wherein R1, R3 and P1 are as defined in claim 1, X is a halogen atom.

9. A method for preparing the compound of formula (e2) comprising subjecting the compound of formula (e1) to a hydrolyzation reaction to generate the compound of formula (e2), wherein the reagent employed for the hydrolysis 15 is an alkali base, and

wherein R1, R3 and P1 are as defined in claim 1.

10. The use of compound (E) according to claim 1 to obtain a compound of formula (D), wherein the compound of 30 formula (E) is subjected to catalytic hydrogenation

wherein R5 is a hydrogen atom or C 1∼C6 alkyl, R1 is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl and n-hexyl; 45 R6 is a hydrogen atom, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl or n-hexyl; P2 is a hydrogen atom, acetyl, trifluoroacetyl, allyloxycarbonyl, t-butyloxycarboryl, trimethylsilyl, tert-butyldimethylsilyl or benzoyl.

11. The use according to claim 10, wherein the catalyst for catalytic hydrogenation may be selected from palladium on 50 carbon, platinum oxide or Raney Ni.

12. The use according to claim 10, further comprising the step of reduction of the compound of formula (D) to a compound of formula (c1),

26 EP 3 015 456 A1

wherein R6 and P2 are as defined in claim 10.

13. The use according to claim 12, wherein the reducing reagent employed is selected from tributyltin hydride, triphenyltin hydride, triethyl silicane, trichlorosilane, sodium borohydride, sodium trimethoxyborohydride, lithium tri-sec-butyl- 15 hydridoborate, potassium tri-sec-butylborohydride, lithium triethylborohydride, diisobutyl aluminium hydride (DIBAH) and sodium bis(2-methoxyethoxy)aluminiumhydride.

14. The use according to claim 10, when R 5 is a hydrogen atom, further comprising the step of addition of alkyl chloroformate before the step of subjecting the carboxyl group of compound (D) to a reduction reaction. 20 15. The use according to claim 12, further comprising the step of converting the compound of formula (c1) to the compound of formula (b1) by removing the carboxyl group,

wherein P2 is as defined in claim 10. 35 16. The use according claim 15, further comprising the step of converting the compound of formula (b1) to the compound of formula (A1) by an alkylation reaction,

wherein R4 is C1~C6 alkyl, and wherein P2 is as defined in claim 10. 50

27 EP 3 015 456 A1

28 EP 3 015 456 A1

29 EP 3 015 456 A1

30 EP 3 015 456 A1

REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• CN 201310261857 [0001] • WO 2009118759 A [0006] • CN 201310580894 [0001] • WO 2004039367 A [0009] [0010] • CN 201410255311 [0001] • WO 2012068234 A [0012]

Non-patent literature cited in the description

• Bioorganic & Medicinal Chemistry Letters, 2011, vol. 21 (12), 3771-3773 [0009] [0010]